1. Field of the Invention
This invention relates to a lock assembly, more particularly to a lock assembly which has at least two lock sections that can be operated successively by a single key.
2. Description of the Related Art
Generally, a conventional lock assembly has a lock section which can be unlocked by means of a key. The conventional lock assembly 10, as shown in FIG. 1, includes a lock shell 11, a key plug 12, and a tumbler means 13.
The lock shell 11 has a front end, a rear end, an accommodation hole 111 which extends from the front end to the rear end of the lock shell 11, and an annular dent portion 112 which is formed in the front end of the lock shell 11.
The key plug 12 is mounted rotatably within the accommodation hole 111 of the lock shell 11 and has a flange 122 which projects outwardly from a front end of the key plug 12 and which lies in the annular dent portion 112 of the lock shell 11 so as to retain the key plug 12 on the lock shell 11 when the key plug 12 is mounted within the accommodation hole 111. The key plug 12 further has a key way 121 which is accessible from the front end thereof for receiving a key 20. Two retaining protrusions 123 project respectively from upper and lower portions of a rear end of the key plug 12 so as to define a retaining space 125 between the inner surfaces of the retaining protrusions 123 for receiving a tailpiece 14 (see FIG. 2) which is used to unlock the lock assembly 10 in a known manner when the tailpiece 14 is rotated synchronously with the key plug 12. Each of the retaining protrusions 123 has an annular groove 124 formed in the curved outer surface thereof. A C-shaped lock element 15 is sleeved securely on the annular grooves 124 of the retaining protrusions 123 of the key plug 12 in order to lock the key plug 12 on the lock shell 11 (see FIG. 2).
The tumbler means 13 includes five outer tumbler holes 131 which are formed in the lock shell 11 to receive five outer tumbler pins 133 and five tumbler springs 134 therein, five inner tumbler holes 132 which are formed radially in the key plug 12 to communicate with the key way 121 and which are aligned respectively with the outer tumbler holes 131 when the lock assembly 10 is at a locked position, and five inner tumbler pins 135 which are received respectively within the inner tumbler holes 132 and which are in contact with the outer tumbler pins 133. Accordingly, the tumbler springs 134 urge the outer and inner tumbler pins 133, 135 toward the key way 121 of the key plug 12 so that the outer tumbler pins 133 are disposed between the junction of the key plug 12 and the lock shell 11. In this way, rotation of the key plug 12 relative to the lock shell 11 is thus prevented by the outer tumbler pins 133, thereby locking the lock assembly 10.
The key 20 includes a handle 21 which is formed integrally with a key body 22. The key body 22 has a plurality of actuating protrusions 23 of different shapes for operating the inner tumbler pins 135 when the key body 22 is inserted into the key way 121 of the key plug 12, thereby disengaging the key plug 12 from lock shell 11 so as to permit rotation of the key plug 12 relative to the lock shell 11 in order to unlock the lock assembly 30, as shown in FIG. 2. However, because the lock assembly 10 has only one key plug 12, a skilled person can easily unlock the conventional lock assembly 10 with the use of a simple tool in a very short time.